The Hard Science of Double Dipping

Every Seinfeld fan knows about the double dip. Now a real study.

Just in time, a scientific report has some new findings that may cause football fans to take a second look at that communal bowl of dip.

The study, to be published later this year in the Journal of Food Safety, is the only one I’ve ever seen to proclaim that it was inspired by an episode of “Seinfeld.” It was conducted as part of a Clemson University program designed to get undergraduate students involved in scientific research. Prof. Paul L. Dawson, a food microbiologist, proposed it after he saw a rerun of a 1993 “Seinfeld” show in which George Costanza is confronted at a funeral reception by Timmy, his girlfriend’s brother, after dipping the same chip twice.
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On average, the students found that three to six double dips transferred about 10,000 bacteria from the eater’s mouth to the remaining dip.

Each cracker picked up between one and two grams of dip. That means that sporadic double dipping in a cup of dip would transfer at least 50 to 100 bacteria from one mouth to another with every bite.

http://www.nytimes.com/2008/01/30/dining/
30curious.html?ref=health

Well that really doesn't seem too surprising. I'm no clean freak so it won't stop me from eating dip at parties. As for being the culprit well I can say I'm not. It's easy enough to just break break large items in half and dip the untouched parts in the dip.
And assuming you're partying with friends why would you embarrass anyone who double dips? Just sanitize yourself with a copious quantity of alcohol.